Billy Connolly has forgotten the punch line to one of his stories, he warns the audience at the start of his very funny new show at Marines Memorial Theatre. Some of the stories don't really have punch lines, he adds, or even endings.

He's as good as his word, which is all to the good in "Billy Connolly: The Man Live," which opened Tuesday and plays through Saturday. Some of Connolly's jokes and anecdotes are pretty funny, but the over-generous heart of his comedy is the man himself - his mimicry, physical dexterity, use of minute comic details, cracking up at his own humor and seeming inability to complete a thought without getting sidetracked.

A mention of the "drug songs" of the 1960s leads the Scottish actor into an explication of one of his favorite four-letter expletives ("if you use it properly"), which somehow veers into inventing names for the "horizontal escalators" in airports (none of his other candidates are printable). For the next several moments he's miming the increasingly hilarious walks of people on those moving walkways, adding a suitcase here or a too-rapid handrail there.

Every moment seems made up on the spot, which may be more than sheer craft. "I haven't done this in ages," Connolly said Tuesday, explaining that he's "been busy being a film star." (The co-star of "Mrs. Brown" will appear next onscreen in "The Hobbit" and "Quartet," opposite Maggie Smith.)

None of the material is familiar from Connolly's two-week run at what was then Post Street Theatre four years ago, except the plentiful use of common expletives as adjectives, nouns and interjections. The costume is the same - black T-shirt with tails and tight striped pants. The great mane of hair and goatee are whiter now that he's "just turned 70" - which occasions a disquisition on "the involuntary noises you start to make" with age.

But the indignities of aging aren't the substance of this show. For the next two-plus hours - without intermission - Connolly spins tales from his early years as a banjo player with his band, the Humblebums, before he made it big in stand-up comedy and then film and TV.

Well not "tales," exactly. Connolly is less a raconteur than what we might call a "digresseur." Each digression keeps getting interrupted by countless others, punctuated by a vacant stare, an abrupt "Right!" and a return to either a previous digression or one of the primary story lines about a gig in Dundee, Glasgow or Belfast or lighting a cigar.

It's all a bit much. As charismatic a comic as Connolly is, his act begins to wear thin after a while, with longer interludes of wondering where it's going between bursts of hilarity. Then it's over, either because the time is up or Connolly has sensed he's losing the crowd. After which he rewards us with an old but very well-told joke about a penile transplant and an elephant.